1. Field of Invention
The present invention relates to a direct current (“DC”) steam plasma torch and a method for reducing the erosion of electrodes thereof.
2. Related Prior Art
Plasma torches have been widely used in the metallurgy of special metal, the making of extremely fine particles and the changing of superficial properties. In the protection of the environment, plasma torches have been used to melt, pyrolyze or gasify flammable or non-flammable toxic waste, lowly radioactive waste, ash from incinerators or perfluorocompounds for de-toxication, volume reduction, solidification or conversion into resources.
As disclosed in U.S. Pat. Nos. 4,587,397 and 4,625,092 issued on 6 May 1986, working gas is only introduced into a DC plasma torch between front and rear electrodes of the DC plasma torch, and the rear electrode is a closed-loop gas supply system. A magnetic field may or may not be provided in the DC plasma torch. Where no magnetic field is provided, an arc does not move in a large area. Therefore, the area for the radiation of heat is small, and the thermal load on the front and rear electrodes are heavy so that the front and rear electrodes can easily be melted. The working gas is dry gas such as air, nitrogen, argon or helium. Where air and nitrogen are used, there may be hazardous byproducts such as NOX.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.